1. Technical Field
This invention relates generally to rotating dynamoelectric machines and more specifically, to an improved arrangement for positioning and mounting the stator assembly of such machines within a surrounding housing.
2. Background Art
Inductor type dynamoelectric machines have been employed, in the past, to realize high-speed operation, particularly for electrical generation. Such machines are generally characterized by a stator which includes both AC armature and DC excitation coils, surrounding a coil-less rotor. Since there are no rotating field or armature coils in this type of dynamoelectric machine, slip rings, brushes and associated connections, common to machines having rotating windings, may be entirely eliminated. This feature, coupled with the typical solid construction of the machine rotor, makes the inductor machine particularly adaptable to high rotational speed applications.
One known version of an inductor type dynamoelectric machine, employs a circumferentially distributed arrangement of "C" or "U" shaped armature elements surrounding a generally cylindrical field coil which in turn encloses a transverse pole magnetic rotor. U.S. Pat. Nos. 437,501, and 2,519,097 and 3,912,958 describe earlier machines of this general design. Such machines typically employed frame mounted hardware for directly supporting the individual components of the stator and suffered from deficiencies attendant to this construction.
A more recent version of such an inductor type machine is disclosed in commonly owned, U.S. Pat. No. 4,786,834, issued Nov. 22, 1988 in the name of James J. Grant, et al. The improvement described therein encompasses a spool-like support structure for supporting the field winding and armature elements from inside and for accurately positioning the armature elements. The spool-like structure is made of non-magnetic material and has a hollow, elongated central portion extending concentrically about a longitudinal axis. This central portion supports a field coil and defines an interior longitudinal passageway for accommodating the insertion of a coaxial rotor. At each end of the central portion, end portions extend radially outward therefrom. Each of these end portions is preferably provided with radially oriented grooves in its axially outermost surface. The grooves are configured to receive and orient legs of generally U-shaped armature core elements arrayed in a circumferentially distributed pattern about the periphery of the spool-like structure. The end portions of the spool-like structure are axially spaced and radially dimensioned, and the grooves in the outer face of each end portion are angularly spaced so as to precisely position the armature elements in three orthogonal directions.
Other features, aspects, and advantages and benefits of this recently developed, highly acclaimed dynamoelectric machine are detailed in U.S. Pat. No. 4,786,834, the disclosure of which is incorporated by reference herein.
The spool-like stator support structure of earlier U.S. Pat. No. 4,786,834 was centered within a housing or frame, radially, by end portion extensions or spokes and axially by spacers located between the end portions of the spool-like structure and end shields of the housing. The stator assembly was interference fit within the housing. This was accomplished by heating the housing so that it thermally expanded before inserting the stator assembly and then allowing the housing to cool and shrink back into interference fit around the stator assembly.
This mounting approach, although it allowed for ready assembly and disassembly of the machine, also suffered from certain limitations. The interference fit required the radial extensions on the end portions of the spool-like support structure to be machined to tight tolerances and also prevented any adjustment or fine tuning of stator assembly position after mounting in the housing. The mounting process required auxiliary heating and cooling steps and equipment, applied stress to the spool-like support structure and did not ensure accurate axial positioning of the complete stator assembly. Accordingly, a new approach for securely and accurately positioning and mounting the stator assembly within the housing, which approach is less difficult, time consuming and expensive to implement, is desirable.